Flashget/Flashgot Downloader vs. Firefox Built In Downloader

I have been using Flashget/Flashgot with Ff for many years, but since using this new computer, I have a problem. (I have installed the same Win 7 ulti from the repository, as on the old computer, and I am using Ff 23.0.1, but also tried other versions to fix the problem, to no avail.)

I use a video recording service and when I try to open a link to a download, I get a Ff Pop Up telling me, that Ff blocks that (download link) pop up. I added that video website to the exceptions of Ff pop up blocker, and when that did not help, I deactivated the Ff pop up blocker completely. Still, no result….

Part two of the problem are the overriding of the Flashget download options by Ff.
In the options of Flashgot, which I have also used without any problem for many years, I have changed from "Ff Built In Downloader" to Flashget as default.

But…. Built In is not impressed and automatically grabs every download.
At other websites I can get around that by a right mouseclick and then choosing flashget from the menu.
Which shows flashget works normal…

On the video website I am talking about, no rightclick is possible, just a normal leftclick in the Ff pop up, which then activates the Built In Downloader, which of course only uses one third the speed of flashget.

(I have installed and uninstalled the three components several times, also used different versions...)

So, I still have these two questions:

How can I force Ff to accept my option choices (to allow pop ups)?

How do I force Ff to accept my Flashgot default choices (to use flashget instead of built in)?

Thank You…

In case you are wondering, why I am asking here…
I have asked everywhere else and no one has an answer….